This book offers a new theory of federalism. The work critically discusses traditional federal theories and builds on theories that focus on the dynamics of federalism. The book offers a definition of federalism and federal organizations that encompass both new and old types of multi-tiered system. Unlike traditional federal theory, it is well-suited to research both multinational and mono-national systems. Also, it takes into account the complexity of these systems, with bodies of governance at the local, regional, national and supranational level. The book is divided in three parts. A first part outlines the contours of dynamic federalism, based on a critical overview of traditional federal theory. The second part develops comprehensive indexes to measure autonomy and cohesion of multi-tiered systems. The third part focuses on the dynamics of federal organizations, with a special focus on institutional hubs for change. The book will be an essential resource for legal, social, economic and political scholars interested in federalism, regionalism and de/centralization.